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Food Allergy

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What are the common food allergens?

In Hong Kong, the 8 most common food allergens include:

  • Milk

  • Egg

  • Fish

  • Shellfish

  • Peanut

  • Tree nuts

  • Soy

  • Wheat/Gluten

Among these shellfish is the most common food allergen in Asia, including Hong Kong. It is also the most common trigger of food-induced anaphylaxis globally, a potentially life-threatening condition.

What is food allergy?

Food allergy is caused by an abnormal immune response to non-harmful substances in the food. Food allergies affect around 1-3% of adults and 4-6% of children worldwide, with recent studies showing that its prevalence is increasing.

The development of food allergies can be divided into the sensitization and reaction phase. The production of allergen-specific IgE during sensitization phase and the degranulation of mast cells in the reaction phase are the key processes involved.​

Currently there is no curative treatment for food allergy. The only way to prevent allergic reactions to food is to strictly avoid food that contains allergens.

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How are food allergies diagnosed?

The diagnostic methods of food allergies include:

  • Medical history of adverse reaction to food

  • Skin prick test

  • Serum allergen-specific IgE test

  • Oral food challenge

IgG testing cannot be used to diagnose food allergies. IgG antibodies are produced by our body as a normal reaction to foreign substances (food). It does not necessarily correspond to clinical symptoms of food allergy.


What are the signs and symptoms?

Some mild to moderate allergic reactions include:

  • Itchiness, rash and/or urticaria (hives) on skin

  • Swelling of face, lips and/or eyes

  • Itchiness of tongue and/or throat

  • Nausea, vomiting, abdominal pain, diarrhoea

Some severe allergic reaction (anaphylaxis) include:

  • Swelling of tongue and/or throat

  • Coughing, difficulty swallowing, noisy breathing, wheezing

  • Hoarse voice, painful swallowing

  • Persistent dizziness or loss of consciousness

  • Pale and floppy (young children)

If the above signs and symptoms occur...

  • Consult a doctor immediately

  • If any of the severe allergic reaction occurs, call 999 immediately for an ambulance to transfer the person to the hospital for prompt medical attention

  • If the person has anti-allergic medications or adrenaline autoinjector with him/her, use the medication according to the doctor's prescription

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